The "Select Land" yellow marker doesn't display underwater, when looking from the outside through the water itsself. Same the other way around... if the camera is positioned underwater, you don't see the selection outside. I am not 100% sure if this is a bug or put on purpose, though I remember it worked in the past and it was much better that way. You should normally be able to see underwater too, to know what you select even under the water level.